20 Million BTU ****************** The heat content of coal varies. Bituminous coal typically has a gross heating value of 30,600,000 BTU per ton. The net heatin…g value is 26,000,000 BTU per ton, assuming 85% efficiency. If you need more precise information, go to the U.S. Department of Energy website at www.doe.gov and search on the heat content of coal. -ecn

Productivity has undoubtedly increased since the 1920s, through better machinery etc., but quantity of production has dropped drastically in the last few decades because m…ost British coal mines have been closed.

China produces almost half of world's coal; Australia exports the most coal; Japan imports the most coal. Top coal producers, according to the World Coal Institute as of 2006 …are: China at 2,482 metric tonsUnited States at 990 metric tonsIndia at 427 metric tonsAustralia at 309 metric tonsSouth Africa at 244 metric tonsRussia at 233 metric tonsIndonesia at 169 metric tonsPoland at 95 metric tonsKazakhstan at 92 metric tonsColombia at 64 metric tons South Africa, Uruguay, Uganda

Unfortunately, there are quite a few. Lebanon sank into civil war in the late 1970s, and has yet to really end the conflict. A civil war (with substantial outside interfer…ence) happened in Angola in the 1970s. Cambodia suffered through a Civil War, the Khmer Rouge, and the Cambodian-Vietnamese War all in the mid 1970s. Burma has been undergoing varying degrees of revolution, civil war, and rebellion for almost 30 years now. Laos also experienced a substantial civil war (as an outgrowth of the Second Indochina War) in the 70s. Both Columbia and Bolivia have been fighting substantial internal guerrilla wars, which have approached civil war status at times. Yugoslavia split in the late 1990s, causing what is usually known as the Balkan War. The war in central Africa in the Congo is generally considered to be the bloodiest conflict since WW2, with over 4 million dead since the mid-1990s (and it's still ongoing) Somalia essentially disintegrated into complete anarchy in the mid 1990s, and hasn't recovered yet. Likewise, Yemen has similarly virtually ceased to be a functioning country. Sri Lanka recently ended a longstanding quasi-civil war again the Tamil Tigers faction. Frankly (and sadly), I'm sure I've missed quite a few.